Effectively striking moving targets with shotgun ammunition requires the shooter to lead the object so that the projectile intercepts the target. Mastering the lead is difficult to accomplish, and requires practice and patience. The present invention enables the shooter to learn to effectively lead the target by using a tracer that is effective in a distance ranging from approximately 10 to 100 meters.
The visibility of an object to the human eye generally depends on the size, distance, speed, color/brightness of the object and atmospheric conditions. Inventors have developed tracers for shotgun shells in an attempt to aid the shooter in visualizing their shot with regard to the target.
Prior tracers can be categorized as non-ignition and ignition type. This invention relates to non-ignition type tracers and, more specifically, chemiluminescent tracers. Prior designs, like those disclosed in U.S. Pat. No. 7,610,857 by the present inventors, use a chemiluminescent platform to produce a trace. Because the brightness of the chemiluminscent reaction is typically constrained by the shelf life requirements of the ammunition, wherein the brighter the chemistry the shorter the shelf life, prior art chemiluniscent tracers are often not bright enough to be seen by the shooter other than in low-light conditions. Most efforts by manufacturers to date have been focused in improving the chemistry with catalysts and the like, in order to accelerate the reaction and/or make it brighter, while maintaining the minimum shelf life requirements dictated by customers. Furthermore, the ballistics of the tracer in U.S. Pat. No. 7,610,857 is such that it travels with the shot for well over 200 meters at speeds typically greater than 330 m/s (1000 ft/s). The speed requirement for shotgun ammunition is driven by the perception that, at higher speeds, the lead is reduced significantly (making it “easier” to hit a moving target) and that a certain speed is required to break a clay target or down a live target (dove, duck, geese, etc.)
Because an object that is stationary or traveling at low speed is more easily visible than one that is traveling at high speed, a simple solution to improve the visibility of an object is to slow it down so the human eye can track it more easily. For tracers, one option is to reduce the amount of propellant in the shotgun cartridge. However, this reduces both the speed of the shot and the speed of the tracer, which creates concerns for shooters, since the shot may travel too slowly to be effective. The present invention overcomes this problem by increasing the air drag/friction on the tracer insert in order to slow it down and make it more visible, without losing accuracy or slowing the shot. The present invention can be used in shotgun shooting ranging from approximately 10 to 70 meters. Further, because the tracer's range is greatly limited, safety concerns are reduced as to any lethal effect of the round in the event of an accident.
Essentially two forms of braking (or drag) forces affect an object during flight: one is caused by friction along the surface of the object; and the other is caused by the dynamic pressure that acts on the projected area of the object perpendicular to the flight path as the object displaces fluid during flight. In the former case, the drag force is proportional to the viscosity of the fluid (air in this case), to the speed of the fluid, to the surface roughness of the object, and to the surface area of the object that is exposed to the flow stream. In the latter case, the drag force is directly proportional to the square of the speed of the fluid and to the projected area of the object; in the case of cylindrical objects, the dynamic drag (or braking) force is therefore proportional to the square of the diameter of the object. In the present invention, both types of drag forces are present, but, because of the high speeds involved and the short flight paths, surface drag forces are smaller than the dynamic pressure forces, and, therefore, this invention relates to the means of increasing the dynamic pressure forces acting on a shotgun tracer to slow it down and thereby make it more visible to the shooter. Ultimately, the level of deceleration achieved is defined by the ratio between the drag force and the mass of the object; in other words, the higher the drag force, the higher the deceleration rate, and the larger the mass of the object, the lower the deceleration rate.
There are several inventions that incorporate a decelerator into a shotgun shot holder (also referred to as a wad). These inventions include U.S. Pat. No. 3,234,877 to Herter; U.S. Pat. No. 3,788,224 to Merritt; U.S. Pat. No. 3,974,775 to Kerzman et al.; and U.S. Pat. No. 4,434,718 to Kopsch et al. In all these patents, the shot holder, or wad, carries the payload, which can be shot-pellets, a sabot or slug, as it travels in the shotgun barrel, protecting the barrel from wear. The walls of the wad are pre-sliced, so that when the wad enters the air stream, its walls extend completely, but not evenly, stopping the wad a short distance from the muzzle of the shotgun, thus allowing the wad to separate from its payload without affecting the trajectory of the payload as it travels towards its intended target. Because the purpose of the sliced walls of the wad is to stop it as soon as possible so that it separates from its payload, the accuracy of the actual trajectory of the wad is erratic and largely irrelevant. The present invention is very different from such prior art since it has a very different application than slowing down a wad (or shot holder) as it carries the payload while traveling through the shotgun barrel, then separating during flight. The present invention, on the other hand, describes a tracer insert, which incorporates a decelerator in the form of several integrated thin-flaps, which, together with the shot pellets, is carried in a wad. Upon firing, the thin-flaps are evenly deployed to slow down the tracer insert during flight, thereby making the tracer visible to the shooter by accurately reflecting the trajectory of the shot in the effective range.